激光成孔技术现状与发展

随着 PCB 对微小孔需求的不断增加,各种微孔加工技术都成为 PCB 界关注的焦点:光致成孔、等离子体蚀孔、激光成孔、甚至机械钻孔,都各有特点。其中,激光成孔适用于各类树脂体系,包括 PI、BT 这类无法加工成光致成孔材料的高性能 PCB 基材,有些激光还具有蚀铜的功能,加之激光形成的孔径小,孔位准,性能价格比可接受,故而,人们更多地把眼光投向激光成孔。1 激光成孔的基本原理和分类激光具有高能量、高方向性等特点,当一束激光通过透镜照射在物体上。

添加剂对高陡岩石边坡人工基质性状的影响

为解决工程技术中的人工基质粘结性、通透性及有机养分问题,对添加水泥、木屑、稻草及泥炭土等的理化性质进行系统测定。结果显示:水泥加入土壤后,不仅导致pH值的显著上升,还引起土壤的硬化及最大持水量的显著降低(P<0.05)。使用酸度矫正液Ⅲ进行基质改良,水泥添加量完全可以超过基质质量的2.0%。木屑和泥炭土的添加,显著提高了土壤持水能力,并从一定程度上缓解了粘结剂引起的土壤硬化(P<0.05)。由于2mm直径的稻草会造成土壤过度松散,可能降低基质的抗侵蚀能力,所以不宜应用。通过试验,确定了进一步深入试验的各添加成分的上限含量。

透湿防水胶布的研制

所研制的透湿防水胶布的结构组成为覆盖胶层、底涂胶层和纺织物层。底涂胶层的成孔材料选用羧甲基纤维素钠的微细粉末，用量约为底涂胶层（浆）胶料的２０％，水煮成孔。底涂胶层单位面积上胶量（干胶）为１００—１１０ｇ·ｍ－２，覆盖胶层单位面积上胶量（干胶）为３０—４０ｇ·ｍ－２，涂制好的胶布厚度为０．３８—０．３９ｍｍ。水煮后的胶布采用卷蒸车硫化罐直接蒸气硫化。成品胶布的通气性（压差为９８Ｐａ）１．５—３ｍＬ·ｃｍ－２·ｍｉｎ－１，透湿度（杯内水，杯外硅胶干燥器，４０℃）１５—２０ｇ·ｍ－２·ｈ－１，耐水压２．９４－３．９２ｋＰａ。

Oxidation behavior of porous Ti_3SiC_2 prepared by reactive synthesis

High-purity porous Ti3SiC2 with a porosity of 54.3%was prepared by reactive synthesis and its oxidation behavior was evaluated under air in the temperature range from 400 to 1000°C.Thermogravimetric analysis and differential scanning calorimetry(TG-DSC),scanning electron microscope(SEM),X-ray diffractometometry(XRD),energy dispersive spectrometer(EDS),Raman spectrum,BET surface area analysis,and pore-parameter testing were applied to the studies of the oxidation kinetics,phase composition,micro morphology,and porous structure parameters of porous Ti3SiC2 before and after oxidation.The results showed that the formation of TiO2 oxidized products with different modifications was the primary factor influencing the oxidation resistance and structural stability of porous Ti3SiC2.Cracks were observed in the samples oxidized in the full temperature range of 400-1000°C because of the growth stress and thermal stress.At 400-600°C,anomalous oxidation with higher kinetics and the aberrant decrement in pore size and permeability were attributed to the occurrence of severe cracking caused by the formation of anatase TiO2.At raised temperatures over 600°C,the cracking phenomena were alleviated by the formation of rutile TiO2,but the outward growth of the oxide scales detrimentally decreased the connectivity of porous Ti3SiC2.

Synthesis of mesoporous carbon as electrode material for supercapacitor by modified template method

The pore structures and electrochemical performances of mesoporous carbons prepared by silica sol template method as electrode material for supercapacitor were investigated. The mean pore size and mass specific capacitance of the mesoporous carbons increase with the increase of mass ratio of silica sol to carbon source （glucose）. A modified template method, combining silica sol template method and ZnCl2 chemical activation method, was proposed to improve the mass specific capacitance of the mesoporous carbon with an improved BET surface area. The correlation of rate capability and pore structure was studied by constant current discharge and electrochemical impedance spectroscopy. A commercially available microporous carbon was used for comparison. The result shows that mesoporous carbon with a larger pore size displays a higher rate capability. Mesoporous carbon synthesized by modified template method has both high mass specific capacitance and good rate capability.

Pore constitution and tortuosity factor of reactively synthesized porous TiAl intermetallic compound

The pore constitution and tortuosity factor of porous TiAl intermetallic were studied on the basis of the variation behavior of pore structure parameters and the discrete particle model. The pore formation mechanism of porous TiAl is mainly ascribed to three aspects: the clearance space in green compact, the diffusive pores in the reaction process and the phase transition pores, resulting in the open porosities of 5.6%, 42.9% and 1.3%, respectively. According to the Hagen-Poiseuille equation, the tortuosity factor of porous TiAl is determined in the range of 1.3-2.2. Based on the discrete particle model and the variation rule of the tortuosity factor, the tortuosity factor depends mainly on the parameters of fabrication constant, particle shape factor, clearance distance and powder particle size. The quantitative relationships among them have been established, which can be used as the basis for adjusting the pore structure of porous intermetallics.

Prins cyclisation of (-)-isopulegol with benzaldehyde over ZSM-5 based micro-mesoporous catalysts for production of pharmaceuticals

Several ZSM-5 derived micro-mesoporous catalysts were investigated in Prins cyclisation of (-)-isopulegol with benzaldehyde acting as a reactant and a solvent for production of heterocyclic oxygen containing 2H-chromene derivatives including the tetrahydropyran structure and exhibiting biological activity. The investigated catalysts were characterized by nitrogen adsorption, ammonia temperature programmed desorption, adsorption-desorption of pyridine and 2,6-di-tert- butylpyridine with Fourier transform infrared spectroscopic control. For the Prins reaction performed at 70℃, the highest yield of the desired product, equal to 67% at complete conversion of (-)-isopulegol, was obtained over a micro-mesoporous catalyst containing an optimum amount of strong acid sites and mesopores, being 12 fold larger than the size of the desired product.

Synthesis and Characterization of Worm-shaped Tubular Lanthanum Aluminum Composite Mesoporous Materials

The lanthanum aluminum mesoporous materials were synthesized using sodium dodecyl sulfate as a template agent by ultrasonic hydrothermal method.The resulting samples were characterized by low angle X-ray diffraction（XRD）,N2 adsorption-desorption studies,transmission electron microscopy（TEM）and surface morphology analysis（SEM）,surface acid（NH3-TPD）,reducibility properties（TPR）,X-ray energy dispersive spectrometer（EDS）and thermogravimetric analysis（TG/DTG）.A l/La composite mesoporous material were synthesized with n（Al）︰n（La）=70︰1.0,80°C of reaction temperature,20 h of reaction time,12 h of crystallization time,650°C of calcination temperature.The specific surface area of the sample is 273.90 m 2 ·g ？1 ,with the average diameter 5.642 nm and pore volume 0.2354 cm 3 ·g ？1 .The samples have mesoporous structure and its particles are similar to a worm-shaped tubular structure.The influence of calcination temperature on the surface physical and chemical properties of Al/La composited mesoporous materials was examined,and the results showed that the acid strength was increased but the amount of acidic sites is decreased as the calcination temperature increased.It was found that the sample calcined at 650°C had appropriate acid content,acid strength and better reducibility.

Synthesis of Thiol-functionalized Mesoporous Materials for Hg2. Trapping

Mesoporous silica materials with uniform channels containing functionalized organic monolayers have been synthesized by grafting a thiol functional group, （3-Mercaptopropyl） trimethoxysilane （MPTMS）. A new approach to heavy metal ion adsorbents based on the covalent grafting of MPTMS groups to the framework pore walls of mesoporous silica molecular sieves has been developed and investigated with regard to hydroxyl group densities, channel dimensions, morphologies and reaction conditions. Results show that the ordered mesostructures of functionalized samples were retained after modification and the thiol functional group was immobilized mainly inside the mesopore channel. The relative surface coverage of the monolayer can be systematically varied up to 95%. The functionalized hybrid materials show exceptional selectivity and capacity for removing mercury from aqueous waste stream with distribution coefficients up to 435,000. The regenerated material show high mercury ion uptake capacity of 2.87 mmol/g （86.5%）.

Mesoporous Silica Materials Synthesized via Sol-Gel Methods Modified with Ionic Liquid and Surfactant Molecules

Mesoporous silica materials were synthesized via a sol-gel method employing a room temperature ionic liquid （1-butyl-3-methylimidazolium tetrafiuoroborate, [bmim][BF4]） as a new solvent medium and further modified with surfactant （hexadecyl-trimethyl-ammonium bromide, CTAB） as a pore templating material. The synthesized samples were characterized by the transmission electron microscopy, X-ray diffraction, and N2 adsorption-desorption techniques. The results indicated that the mesoporous silica synthesized by using [bmim][BF4] and CTAB as mixed templates showed better mesostructural order and smaller pore size, compared with mesoporous silica materials synthesized by using single [bmim][BF4] as template under the same conditions. This indicates that the presence of surfactant can affect the microstructures of silica prepared by＇the present synthesis method.

Hierarchical porous metal ferrite ball-in-ball hollow spheres： General synthesis, formation mechanism, and high performance as anode materials for Li-ion batteries

High yields of CoFe204, NiFe204 and CdFe204 hierarchical porous ball-in-ball hollow spheres have been achieved using hydrothermal synthesis followed by calcination. The mechanism of formation is shown to involve an in situ carbonaceous-template process. Hierarchical porous CoFe2O4 hollow spheres with different numbers of shells can be obtained by altering the synthesis conditions. The electrochemical properties of the resulting CoFe2O4 electrodes have been compared, using different binders. The as-obtained CoFe2O4 and NiFe2O4 have relatively high reversible discharge capacity and good rate retention performance which make them promising materials for use as anode materials in lithium ion batteries.

Hierarchically porous carbon/red phosphorus composite for high-capacity sodium-ion battery anode

Red phosphorus has received remarkable attention as a promising anode material for sodium ion batteries(NIBs) due to its high theoretical capacity. However, its practical application has been impeded by its intrinsic low electronic conductivity and large volume variations during sodiation/desodiation process. Here, we design a composite to confine nanosized red phosphorus into the hierarchically porous carbon(HPC) walls by a vaporization-condensation strategy. The mass loading of P in the HPC/P composite is optimized to deliver a reversible specific capacity of 2,202 m Ah/gpbased on the mass of red P(836 m Ah/gcompositebased on the total composite mass), a high capacity retention over 77% after100 cycles, and excellent rate performance of 929 m Ah/gpat 2 C. The hierarchical porous carbon serves as the conductive networks, downsize the red phosphorus to nanoscale, and provide free space to accommodate the large volume expansions. The suppressed mechanical failure of the red phosphorus also enhances the stability of solid-electrolyte interface(SEI) layer, which is confirmed by the microscopy and impedance spectroscopy after the cycling tests. Our studies provide a feasible approach for potentially viable high-capacity NIB anode.

Rapid room-temperature synthesis of hierarchical porous zeolitic imidazolate frameworks with high space-time yield

Hierarchical porous zeolitic imidazolate frameworks （ZIFs） have potential for adsorption, catalysis and chemical sensing applications. Ultrafast synthesis of ZIFs at room temperature and pressure is particularly desirable for large-scale industrial production. Here, we developed a green and versatile method using organic amines as supramolecular templates （organic amine-template） to rapidly synthesize hierarchical porous ZIFs （ZIF-8, ZIF-61 and ZIF-90） at room temperature and pressure. The synthesis time was reduced dramatically to within 1 min, and the resulting ZIFs had multimodal hierarchical porous structures with mesopores/ macropores interconnected with micropores. Notably, the space-time yield （STY） of hierarchical porous ZIF-8 was up to 1.29×10^4 kg m^-3 d^-1, which is more than three times higher than that reported using other methods. Furthermore, the morphologies and porosities of the produced ZIFs could be readily tuned by controlling the synthesis time or type of organic amine. The organic amine played two roles in the synthesis： （1） a protonation agent to deprotonate organic ligands, facilitating the formation of ZIF crystals, and （2） an structure directing agent to direct mesopore/macropore formation. The resulting hierarchical porous ZIF-8 exhibited enhanced uptake capacities and diffusion rates for guest molecules relative to its microporous counterpart. This work provides a new direction for the green and efficient synthesis of various hierarchical porous ZIFs with high STYs for a wide range of applications.

Comparison of GTN Damage Models for Sheet Metal Forming

The Gurson-Tvergaard-Needleman(GTN) damage model was developed basing on anisotropic yield criterion to predict the damage evolution for anisotropic voided ductile materials.Hill's quadratic anisotropic yield criterion(1948) and Barlat's 3-component anisotropic yield criterion(1989) were used to describe the anisotropy of the matrix.User defined subroutines were developed using the above models.Taking the benchmark of NUMISHEET'93 square cup deep drawing as an example, the effect of matrix plastic anisotropy on a ductile material was studied.The predicted result by Barlat'89-GTN model has a better agreement with the experimental data than that by Hill'48-GTN and the original GTN model.

Post-synthesis pore expansion of mesoporous silica SBA-15 in the organic template removal via solvothermal treatment

The synthesis of mesoporous material SBA-15 has been extensively reported in the past decades, which possesses a pore diameter of 6-8 nm on average. Here, a simple post-synthesis procedure has been developed to synthesize SBA-15 with further expanded pore diameter to above 10 nm simply by a solvothermal treatment replacing traditional hydrothermal step for mesopore template removal, which results in efficient pore expansion and the significantly promoted condensation of silica framework as well. This facile approach is believed applicable for pore expansions of other kinds of mesoporous silica materials.

Controlled synthesis and shape-dependent electromagnetic wave absorption characteristics of porous Fe_3O_4 sub-micro particles

Porous Fe3O4 sub-micro particles with sphere-like, cube-like and walnut-like morphologies were obtained by a two-step process, and the electromagnetic properties of the Fe3O4 particle/wax composites were investigated. The reflect loss was less than -20 dB for all of the composites in different frequency ranges. The cube-like and walnut-like Fe3O4 composites exhibit improved complex permittivity and permeability and dual-frequency and wide bandwidth absorption characteristics, which is mainly attributed to the larger shape anisotropy. Such a high absorption property indicates that these porous Fe3O4 particles with various morphologies are very promising for electromagnetic wave absorptive materials.